Electrical apparatus often requires a protective housing of some kind, particularly in situations where the apparatus is exposed to the movement of people or other kinds of traffic which might result in accidental damage to the apparatus. Also, electrical apparatus generates heat, due to energy losses inside the circuitry, and since overheating both reduces the level of performance of the equipment and shortens its useful life, appropriate means must be provided for dissipating that heat.
Typical examples are the familiar television receiver and computer monitor, each of which contains a cathode-ray tube operating at a high voltage level. Plastic material is now commonly used to fabricate the housing for this type of equipment. Openings are provided in the housing, generally at or near its upper surface, so that air which is warmed inside the housing will have an opportunity to flow upward and escape from the housing, thus carrying with it the undesired excess heat.
There is, however, a further problem which hitherto appears to have escaped attention. This is the occasional instance of an office worker setting a coffee cup or other drink container on top of the housing, when suddenly, and unexpectedly, the container spills a quantity of liquid which then flows downward through the cooling openings and into the very equipment that the housing was designed to protect. Needless to say, the undesired presence of liquid in electrical circuitry can cause short circuits and other difficulties.